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Inside Politics
Defense Cross-Examines Forensic Pathologist In Chauvin Trial. Aired 12:30-1p ET
Aired April 09, 2021 - 12:30 ET
THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.
[12:30:00]
ERIC NELSON, DEFENSE ATTORNEY: And do you have to have myocyte necrosis to cause sudden death?
THOMAS: No, you don't have to have myocyte necrosis.
NELSON: OK. And would you say that hypoxia is the absence of oxygen, agreed?
THOMAS: Yes.
NELSON: And can hypoxia of the heart cause sudden death by other means?
THOMAS: Hypoxia, hypoxia means low oxygen, sorry. And your question is can low oxygen to the heart cause sudden death through an arrhythmia, I presume? Yes.
NELSON: OK. What would you -- how would you describe the conduction system of the heart?
THOMAS: The way the heart beats, the lub dub, is that there are electrical currents that go through the heart muscle. And normally, there's a certain sequence in which the heart muscle will -- muscles will fire. And that's called the conduction system through which the electrical impulses flow. And that's what keeps the heart beating in a regular rhythm, that beat, beat, beat. And, yes, that's the conduction system.
NELSON: So what happens if the conduction system is impaired?
THOMAS: Then you can get what's called an arrhythmia or abnormal beating of the heart.
NELSON: And that can result in sudden death?
THOMAS: It can, yes.
NELSON: Which artery is supplies that kind of like that pacemaker of the heart? THOMAS: Oh, it probably is variable from person to person. I mean, I think the coronary artery that we consider the most important usually is the left anterior descending coronary artery. But there's a lot of individual variability.
NELSON: Can you -- what about the right corner artery?
THOMAS: That, I mean, it just it really depends on any given person, which part of the heart is supplied by their particular distribution.
NELSON: OK. And in Mr. Floyd's autopsy, the right coronary artery, Dr. Baker determined had a 90 percent occlusion, correct?
THOMAS: Ninety percent narrowing, yes.
NELSON: When someone is exerting themselves, does that make the heart work harder?
THOMAS: Yes.
NELSON: Does that mean that more blood oxygen, it needs more blood to function, the heart needs more blood to function at that time?
THOMAS: Yes.
NELSON: It's kind of like when we think about exerting anything like jogging, running, the heart needs more blood and hence more oxygen in order to function properly, right?
THOMAS: Yes.
NELSON: You also describe the fight or flight kind of the physiology of that in your consideration, right?
THOMAS: Yes, the physiological stress.
NELSON: Right. And the physiological stress produces adrenaline, right?
THOMAS: Yes.
NELSON: And that also causes the heart to work harder?
THOMAS: Yes.
NELSON: And therefore need more blood?
THOMAS: Yes.
NELSON: And more oxygen?
THOMAS: Yes.
NELSON: So let me ask you this, in this particular case, right? We have a heart that is at least above average, right? Needing more blood, we have a heart with a occluded right coronary artery, right? THOMAS: Narrow.
NELSON: Narrowed. We have a heart that the left anterior descending artery also had a 75 percent narrowing, right?
THOMAS: Yes.
NELSON: And so you have, you know, and then you have an exertion of stress producing adrenaline, right?
THOMAS: Yes.
NELSON: So the heart has to work very, very hard in this case, fair to say?
THOMAS: Yes.
NELSON: Let's take the police out of this. And I'm going to ask you a hypothetical. Let's assume you found Mr. Floyd dead in his residence, no police involvement, no drugs, right, the only thing you found would be these facts about his heart. What would you conclude to be the cause of death?
THOMAS: In that very narrow set of circumstances, I would probably conclude that the cause of death was his heart disease.
NELSON: So have you as a forensic pathologist, ever certified a death due to atherosclerotic cardiovascular disease?
[12:35:04]
THOMAS: Probably thousands of times, yes.
NELSON: Similar to -- with similar degrees of narrowing of the arteries?
THOMAS: Yes.
NELSON: Have you ever certified a death due to hypertensive cardiomegaly? I'm trying to --
THOMAS: Yes, hypertensive cardiovascular disease, yes, absolutely.
NELSON: With a heart at this weight or even smaller?
THOMAS: Well, if it was, again, in this setting where that was the only abnormal finding, then I would probably go with that, yes.
NELSON: So one of the things that has to be considered in this particular case is Mr. Floyd's heart, right?
THOMAS: Yes.
NELSON: And even without any sort of an exertion, again, take the exertion out of it, take the police out of it, take the drugs out of it, that's a potential cause of death that needs to be considered? THOMAS: Yes.
NELSON: Now, you discussed the abrasions that you saw on the jury saw pictures of, you would agree that the abrasions are in a left to right pattern?
THOMAS: Meaning there are more on the left than on the right?
NELSON: Right.
THOMAS: On his face, yes, on his shoulder, yes. And then he had the abrasions on his right hands.
NELSON: And even in terms of the pattern of the abrasion, there's up and down abrasion, like an abrasion could go from the bottom of my body up or it could go from left to right, right?
THOMAS: Yes. I guess I didn't really focus on what direction the abrasions were going in that sense.
NELSON: OK. And that's fine. But you would agree that one possible way that some of, at least some of these abrasions occurred would be when Mr. Floyd was initially put down on the ground?
THOMAS: I guess they could, yes.
NELSON: Right. And not all of those abrasions necessarily occurred while Mr. Floyd was in the prone position, right?
THOMAS: It's hard to answer, let's say.
NELSON: Right. It's hard to answer when the abrasions were there --
THOMAS: Right.
NELSON: -- and what caused the abrasions, right?
THOMAS: Right, right.
NELSON: And if someone was being held down with all -- with the weight of three people, would you expect those to be more punk tile in their nature or like, in, you know, with the lines and movements?
THOMAS: Oh, gosh, there are too many variables there, I would say.
NELSON: OK. Now, you ultimately determined that this case was an asphyxiation essentially?
THOMAS: Yes, that that was the primary mechanism.
NELSON: Right. And asphyxiation is simply the lack of oxygen to the brain?
THOMAS: Yes, low oxygen, inadequate oxygen.
NELSON: Inadequate oxygen to the brain specifically? THOMAS: Yes.
NELSON: And in terms of asphyxiation, you would agree that there are multiple things that can cause asphyxiation?
THOMAS: Yes.
NELSON: So you use the reference to someone being strangled, right?
THOMAS: Yes.
NELSON: So if I came up to you and I strangle, you know, or I strangle the person, put my hands around their neck, there are certain things that you would expect to see, right?
THOMAS: Sometimes you do, yes. And that's great when you do.
NELSON: Right.
THOMAS: You don't always, but.
NELSON: And those would be things like a broken hyoid bone?
THOMAS: Yes.
NELSON: Right? The petechial hemorrhaging that you discussed?
THOMAS: Yes.
NELSON: And in an asphyxia death, there are oftentimes, frequently those types of signs available, right?
THOMAS: Well, it really depends on the mechanism of asphyxia.
NELSON: OK. So let's go back to the mechanism of asphyxia. You describe that strangling would be one?
THOMAS: Yes.
NELSON: Hanging would be -- could be one.
THOMAS: Yes.
NELSON: Right? You've described positional or mechanical asphyxia?
THOMAS: Those are types, yes.
NELSON: Yes. Positional being, you know, based on the position of the body mechanical, being something using some sort of device to asphyxiate someone?
THOMAS: Oh, well, we haven't really talked a lot about position on mechanical. I mean, there's all kinds of things under both of those that can cause low oxygen.
NELSON: And one of the things that can cause in this a low oxygen to the brain is the use of controlled substances, correct?
[12:40:00]
THOMAS: Well, eventually, yes, yes.
NELSON: So someone can ingest a particular type of a controlled substance, that particular substance could affect the diaphragm, right, basically?
THOMAS: It affects the -- some controlled substances affect the ability to breathe, which then decreases the oxygen, which then leads to low oxygen, yes.
NELSON: Right. And that's essentially, what you're saying is, is that there in this particular case, as I understand we put in my notes is that essentially what happens is, there was some event that happened that resulted in a decrease of oxygen to the brain and that resulted in death?
THOMAS: Yes.
NELSON: And that's essentially what asphyxia is generally?
THOMAS: Inadequate oxygen, yes.
NELSON: Right. OK. And you were asked a series of questions about some studies in terms of I think they're called the drought of San Diego or something?
THOMAS: Yes, Dr. Chance (ph).
NELSON: Dr. Chance (ph), right. Yes. Are you familiar with the Journal of Forensic and Legal Medicine?
THOMAS: Yes.
NELSON: Now, you testified that some of the problems with the Chance (ph) studies were that they were in laboratory -- lab -- laboratory settings, sorry, laboratory settings, that they were controlled environments, healthy individuals, et cetera, right?
THOMAS: Yes.
NELSON: Are you familiar with the work of Dr. Christine Hall, and her paper incidence and outcome of prone positioning following police use of force in a perspective, consecutive cohort of subjects?
THOMAS: Is that the one from Canada?
NELSON: Yes.
THOMAS: Yes.
NELSON: And that was essentially an analysis of actual police encounters, correct?
THOMAS: Yes, in Canada.
NELSON: In Canada, understood. But they actually that study, they go through and they look at the number of police citizen interactions, correct?
THOMAS: Yes.
NELSON: And then from those police citizen interactions, they further go into look at how many involve being placed in the prone position or a non-prone position, correct?
THOMAS: Yes.
NELSON: They consider various actual real life variables, agreed?
THOMAS: Yes.
NELSON: And including drugs, whether drugs were on board whether the length of time to a certain extent that someone was in a -- in the prone position, agreed?
THOMAS: Yes.
NELSON: And ultimately, they analyzed about -- it was about 3,000 prone positional placements?
THOMAS: Yes.
NELSON: Out of a total of like 1.1 million police interactions?
THOMAS: Yes.
NELSON: So 1.1 million police interactions, resulting in about 3,000 prone position, prone position arrests, that those prone position -- these are real people, real incidents, right?
THOMAS: Yes.
NELSON: And in those 3,000 or so interactions, there were no deaths that occurred?
THOMAS: Isn't that amazing. When you consider that virtually every forensic pathologist in the United States has probably had an officer involved death like this. How did they -- it utterly baffles me, which is why I kept saying Canada, because I think I don't know what's different but.
NELSON: -- this time is in our responsible. So the -- let me ask you, in terms of hypoxia, can you do -- again define hypoxia?
THOMAS: Low oxygen.
NELSON: Right. And which organ is more sensitive to the lack of oxygen, the brain?
THOMAS: The brain. NELSON: The brain?
THOMAS: Absolutely.
NELSON: The brain is the most -- it needs the most oxygen, right?
THOMAS: Yes.
NELSON: And that's because it's doing millions of things simultaneously, right, agreed?
THOMAS: Yes. I'm sure there's lots of reasons metabolically why it needs oxygen.
NELSON: Right. I think a previous witness testified that it takes about 20 percent of the body's oxygen supply to function, right?
THOMAS: That sounds fair, right, yes.
NELSON: But the heart also needs oxygen, right?
THOMAS: Yes.
NELSON: So in terms of the professional standards for determining an asphyxia death, is it true that you have to first exclude all natural and non-natural cases or causes of death?
[12:45:13]
THOMAS: Well, you can have natural and non-natural causes of low oxygen. So, I'm sorry, I guess I don't understand.
NELSON: Sure. There's a criteria that's established for making a determination of positional asphyxia as a cause of death, right?
THOMAS: Well, I'm not really sure what, I'm sorry, I just I don't understand that.
NELSON: Fair enough. Is the prone position in and of itself inherently dangerous?
THOMAS: Not if there are no other factors.
NELSON: OK. So the prone position is examined and used in a lot of different settings, right?
THOMAS: Correct.
NELSON: I mean, even in hospitals in the treatment of say, COVID, the prone position is used, is used?
THOMAS: Correct.
NELSON: And in those circumstances, being in a prone position is not inherently dangerous, right?
THOMAS: Yes.
NELSON: Right. I mean, chiropractors put people in the prone position, right?
THOMAS: Yes.
NELSON: Massage therapists put people in the prone position, right?
THOMAS: Yes.
NELSON: So the prone position, I'm just talking, generally speaking, no other factors, the prone position in and of itself is not inherently dangerous, right?
THOMAS: Right.
NELSON: Is the prone position on concrete, inherently dangerous?
THOMAS: Again, with no other factors, as long as someone can breathe, no.
NELSON: Right. I could be laying by the pool in Florida, right?
THOMAS: Right.
NELSON: On my stomach in the prone position not inherently dangerous?
THOMAS: Right.
NELSON: Do you know or did you -- can take into consideration Mr. Chauvin's weight in your analysis?
THOMAS: Oh, I'm aware of his weight. I would say, I took it into some consideration, but it wasn't a major factor one way or the other.
NELSON: OK. You reviewed all of the videos, right?
THOMAS: Yes.
NELSON: And it's fair to say that portions of his weight were placed on Mr. Floyd's body at a different distribution?
THOMAS: Yes.
NELSON: And, ultimately, in terms of the autopsy that can -- Dr. Baker conducted in terms of the area in the shoulders, the back in the neck, no bruising was found, right?
THOMAS: Right.
NELSON: In your experience as a forensic pathologist, if someone is placing a significant amount of weight on a person's area for a prolonged period of time, would you expect to see bruising?
THOMAS: You might or might not, it's so variable.
NELSON: OK. And you would agree that there are no abrasions or bruising described in the autopsy in the neck area of Mr. Floyd?
THOMAS: Correct.
NELSON: There's no bleeding into the muscles in his back, right?
THOMAS: Correct.
NELSON: You would agree that the knee is sort of a pointy or a more protuberant part of the body?
THOMAS: I guess so.
NELSON: OK.
THOMAS: Kind of flat on top because of the patella but.
NELSON: Right. And when we talk about the shin, the shin bone, the shin bone itself, there's not a lot in between the skin and the shin bone, right?
THOMAS: That is true, yes.
NELSON: And it's sort of a triangular shape, right?
THOMAS: Yes.
NELSON: And again, along Mr. Floyd's back, there's no long bruise consistent with a shin bone, right?
THOMAS: Right.
NELSON: And there's no more circular bruise consistent with the kneecap?
THOMAS: Right.
NELSON: You've reviewed obviously a lot of strangulation type cases in those -- in your career?
[12:50:07]
THOMAS: Yes.
NELSON: Strangulation with the hands, right?
THOMAS: Primarily manual, but also ligature.
NELSON: Right. Ligature being like a rope or a phone cord or something?
THOMAS: Exactly.
NELSON: And in those manual strangulation cases, the pressure that's exerted in that will frequently leave bruises, fingerprint size bruises, right?
THOMAS: Frequently, but not always.
NELSON: And ultimately, what increases the likelihood of seeing a bruise is the amount of force that's applied, right?
THOMAS: You know, I don't know what all the factors are, whether it's fragility of the vessels, whether it's the length of time, whether it's the force, whether it's the location, I think there are lots of variables.
NELSON: So --
THOMAS: And everyone bruises is different one.
NELSON: So yesterday, depends on what medications they may take, right?
THOMAS: Right, right.
NELSON: So yesterday, there was an analysis or an analogy to sitting on a church bench, and you don't bruise you're behind.
THOMAS: And that can feel long.
NELSON: Would it be different if you're sitting on a church bench under with a baseball, for example, underneath your butt?
THOMAS: I really couldn't say.
NELSON: All right. So in terms of Dr. Baker's autopsy, you would agree that there's really no objective evidence showing any pressure to the back of Mr. Floyd?
THOMAS: There is nothing at the autopsy. That's correct.
NELSON: Did you find or did Dr. Baker find hypoxic changes in his brain?
THOMAS: He died too quickly for that to show up.
NELSON: And that's when we talk about the lack of ischemic hypoxia, correct? Dr. Baker noted a lack of ischemic hypoxia.
THOMAS: I don't remember his exact words, but you're describing lack of ischemic changes in the neurons?
NELSON: Correct.
THOMAS: Yes.
NELSON: In the brain.
THOMAS: Yes, because that has to happen over a period of time.
NELSON: OK. And when someone is experiencing that shortness of oxygen, or that lack of oxygen to the brain, that will frequently lead to certain symptoms, right? THOMAS: Yes.
NELSON: Confusion is one?
THOMAS: That could be, yes.
NELSON: Restlessness?
THOMAS: It could be, yes.
NELSON: Shortness of breath?
THOMAS: It could be.
NELSON: Visual changes?
THOMAS: It could be.
NELSON: Incoherent speaking?
THOMAS: It could be.
NELSON: So to your knowledge, did Mr. Floyd in the videos that you observed ever complain of these visual change -- any visual changes?
THOMAS: No.
NELSON: Did he appeared to be confused to you?
THOMAS: So what time, I guess what time period are we talking about, sorry?
NELSON: Sure. That helps maybe if we narrow down that up. The nine minutes, during the nine minutes that Mr. Floyd was restrained did he appear confused to you?
THOMAS: Oh, gosh. How do you describe his behavior?
NELSON: Well, I mean, did he, he was articulating that he was in pain, right?
THOMAS: Yes. And then he couldn't breathe. And he calls for his mother. And he says he loves people. I mean, you might interpret that as confusion or you might interpret it a different way.
NELSON: Did he appear to be breathing during this timeframe?
THOMAS: Not effectively.
NELSON: Do you know how many breaths per minute?
THOMAS: No.
NELSON: If one expert indicated it was at a rate of 22 breathes per minute, would you disagree?
THOMAS: I would have no way of assessing that.
NELSON: When someone is hypoxic, they start breathing faster, right?
THOMAS: That can be a mechanism of trying to balance.
NELSON: At least for the first five minutes or so Mr. Floyd was talking, right?
THOMAS: Well, again --
NELSON: Did talking, yes or no, he was talking?
[12:55:01]
THOMAS: He was, yes. There was -- there were words, yes.
NELSON: So we had an open airway.
THOMAS: Yes.
NELSON: And you would agree that or would you agree that at some point, he went limp, right?
THOMAS: Yes.
NELSON: And would you describe what you saw as the progression of hypoxia in that instance, at the point he goes limp?
THOMAS: That is certainly a good explanation for it, yes.
NELSON: OK. Was not a sudden hypoxic event, right?
THOMAS: That is my interpretation, yes.
NELSON: You would agree that if he was progressively growing hypoxic, you would expect whole body hypoxia? I'll rephrase my question.
THOMAS: Yes, sorry.
NELSON: I'm not a doctor. So I have to rely on my notes quite a bit. So if he was progressively suffering from whole body hypoxia, the brain would be the first thing that would have show signs of hypoxia?
THOMAS: Oh, I see. Yes, yes, the brain is the most sensitive.
NELSON: And you would agree that that would not occur in a matter of seconds, but it would take a matter of minutes, right?
THOMAS: Correct.
NELSON: And asphyxia due to position or compression that prevents air from getting into the lungs, right?
THOMAS: Yes.
NELSON: And that leads to what we would call a global hypoxia? THOMAS: I haven't really used that word, global.
NELSON: OK. Whole body hypoxia?
THOMAS: I mean if there's inadequate oxygen, the blood flows everywhere. So I guess that's what you're talking about.
NELSON: But the brain is the first thing to show symptoms of hypoxia?
THOMAS: Right, that's the most sensitive organ.
NELSON: And in this particular case, where you have a 90 percent stenosis of the right coronary artery, that's going to be limiting oxygen to the heart, right?
THOMAS: Yes.
NELSON: And he has a big heart, right?
THOMAS: Yes.
NELSON: Needs more blood?
THOMAS: Yes.
NELSON: And adrenaline speeds up the heart?
THOMAS: Yes.
NELSON: Methamphetamine speeds up the heart?
THOMAS: It can, yes.
NELSON: So, methamphetamine and adrenaline cause the work to -- the heart to work harder?
THOMAS: It is, yes.
NELSON: And increases the hearts oxygen needs?
THOMAS: Yes.
NELSON: And at what point does the stenosis in the left and right coronary arteries become critical and cause the heart to stop, generally?
THOMAS: Oh, as of -- are you asking that same question about as a forensic pathologist, what degree of narrowing do we consider potentially fatal?
NELSON: Right.
THOMAS: Seventy, 75 percent and above.
NELSON: Now, in terms of drug use, right, you obviously were aware based on the toxicology that Mr. Floyd had certain drugs in his system, right?
THOMAS: Yes.
NELSON: And so when we say onboard, that means in the system?
THOMAS: Yes.
NELSON: OK. Would you describe the use as of, as you know, based on the information that you have, as sort of a binge use of drugs?
THOMAS: Oh, I guess I couldn't, I couldn't answer that.
NELSON: All right. Are you familiar with drug use taken or used intrarectally?
THOMAS: I agree with that, yes.
NELSON: Yes. And that increases or speeds up the distribution of controlled substances in a person?
THOMAS: It speeds up absorption, yes.
NELSON: OK. So the effects would be felt much faster?
THOMAS: Yes, they could.
NELSON: In a case where you have a person who is experiencing cardiac arrest, right, and they're put in an ambulance and taken to the hospital for recitation there often there's I.V.s that are placed in a person, right?
[13:00:06]
THOMAS: Yes.
NELSON: And those I.V.s contained saline?
